1. Field of the Invention
This invention relates to drying method and apparatus to be used after a washing stage for draining and drying a wet work of metal, glass, plastics etc. by the use of hot D.I. (deionized) water to dispel water droplets completely from the work surface, and more particularly to a method and an apparatus of high precision drying capable of lifting a work out of a hot D.I. water bath free of disturbance of the water surface by air bubbles.
2. Description of Prior Art
For example, Japanese Laid-Open Patent Application No. 58-184479 discloses a draining and drying method in which a flat plate-like article with a smooth surface of metal, glass, plastics or the like is put in a bath of heated water or in a bath of pure or D.I. water and then lifted out of the bath at a predetermined speed based on an empirical value as determined article by article.
Also disclosed in Japanese Laid-Open Patent Application No. 64-53549 is a drying method with hot D.I. water, wherein a wet workpiece which has come out of a washing stage is immersed in hot D.I. water of a predetermined temperature and then lifted up slowly to dry the workpiece by its own heat.
In such a drying operation using a hot D.I. water bath, it is an utmost importance to maintain the water surface always in a still state without rippling the water surface, because the pull-out speed of the work relative to the water surface will be varied to deteriorate the drying accuracy when the water surface is disturbed by waves. Namely, when the water surface is moved up and down by waves, the work pull-out speed relative to the water surface becomes faster or slower, bringing the same portion of the work irregularly into repeated contact with the water surface to increase the possibilities of staining and uneven drying of the work surface.
In an actual hot D.I. water bath drying operation, there has been a problem that, when heating D.I. water by the use of a heater to prepare hot D.I. water, the air bubbles which are generated on the surface of the heater or in hot D.I. water creep into a hot D.I. water bath along with the feed water and float up to the water surface to cause rippling of the water surface. Therefore, when drying a work with use of hot D.I. water, it is necessary to prevent rippling of the water surface which is caused by air bubbles.